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<head>
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<title>无标题文档</title>
<style type="text/css">
.layer1{height:100px;}
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	   .layer1-4{clear:both;}
.layer2{height:100px;width:100%;background:#396;}
.layer3{height:100px;width:100%;background:#FC0;}
</style>
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<body>
<div class=layer1>
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    <div class=layer1-2></div>
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</div>

<div class=layer2></div>

<div class=layer3></div>

</body>
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